Electron beam discharge device having improved electron gun structure

ABSTRACT

A cathode ray tube is provided having a gun comprising a cathode, grid, focusing electrodes, and deflection electrodes constructed as a cage assembly with mica spacers between the electrodes to insulate the electrodes from one another and to accurately position the gun in a constant diameter portion of the tube.

I Umted States Patent 1151 3,660,707

Rate, Jr. [4 1 May 2, 1972 s41 ELECTRON BEAM DISCHARGE 2,227,087 12/1940 Hinsch ..313 s0 x DEVICE HAVING IMPROVED ELECTRON GUN STRUCTURE FOREIGN PATENTS OR APPLICATIONS 483,679 4/1938 Great Britain ..313/82 [72] Invent Edward Owensbm 1,260,371 3/1961 France ..313/254 [73] Assignee: General Electric Company Primary Examiner-Robert Sega] 15 1970 [22] Ffled Jan Attorney-Nathan J. Comfeld, John P. Taylor, Frank L. Neu- [21] Appl. No.: 3,051 hauser, Oscar B, Waddell and Joseph B. Forman 521 US. Cl. ..313/80, 313/82 R [571 ABSTRACT [51] InLCl. ...H0lj 29/74, HOlj 29/02 A cathode ray tube is provided having a gun comprising a [58] FEM of Search ..3l3/254, 252, 80 cathode grid ng electrodes and deflection electrodes constructed as a cage assembly with mica spacers between the [56] References Cited electrodes to insulate the electrodes from one another and to UNITED STATES PATENTS accurately position the gun in a constant diameter portion of the tube. 2,064,98l 12/1936 Knoll ..3l3/82 OLarte et al ..3l3/82 1 Claims, 5 Drawing Figures Patented May 2, 1972 3,660,707

INVENTOR! EDWARD T. RATE,JR.

HIS ATTORNEY.

ELECTRON BEAM DISCHARGE DEVICE HAVING IMPROVED ELECTRON GUN STRUCTURE BACKGROUND OF THE INVENTION This invention relates to cathode ray tubes. More particularly this invention relates to the gun structure of a cathode ray tube.

Cathode ray tube electron gun construction normally consists of embedding into glass support rods, pins or claw-shaped straps that are welded to the plates, cups, or cylinders comprising the electrodes of the gun. The position and alignment of the electrodes with respect to each other and the rigidity of the structure is the function of the glass rods. The method of assembly normally requires that the electrodes be accurately positioned in a beading tool; the glass rods heated until they soften; and the beading tool manipulated so that projecting pins on the electrodes are embedded in the soft glass. The total diameter of the gun assembly is then equal to the diameter of the electrodes plus the external projections and the diameters of the opposing glass rods. This total diameter then determines the minimum inner diameter of the neck of the tube. Positioning and retention of the electron gun in the tube is conventionally done by the welding of spring steel snubbers around the periphery of the electron gun to contact the inner surface of the neck.

SUMMARY OF THE INVENTION Accordingly, it is an object of the invention to provide a cathode ray tube having an improved gun structure.

It is another object of the invention to provide a compact cathode ray tube having a gun of overall reduced diameter.

It is yet another object of the invention to provide a cathode ray tube having a compact, inexpensive, easily assembled gun structure having self-alignment means thereon. These and other objects of the invention will become further apparent from the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of the invention.

FIG. 2 is a vertically sectioned view of gun assembly.

FIG. 3 is a exploded view of the invention.

FIG. 4 is a section view of FIG. 1 taken along lines IV-IV. FIG. 5 is a section view of FIG. 1 taken along lines V-V.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1 a cathode ray tube is generally indicated at 2 having a cylindrical glass envelope 4 in which a gun assembly is mounted adjacent one end. At the opposite end of the tube on an end wall 6, a target 8 is located comprising a phosphor coating deposited on the inner surface of end wall 6. Pins 12 provide electrical communication with the various electrodes comprising gun assembly 10.

Gun assembly 10 comprises a stack of electrodes comprising a grid-cathode assembly 40, an einzel focus lens 70, and deflection plates 100, 110, I20, and 130 for deflecting the electron beam in both the X and Y planes. These electrodes are separated by insulators which, together with the electrodes, are radially and longitudinally maintained in alignment by insulating tubes 20. In the preferred embodiment, four glass tubes are used and are angularly spaced apart to form a square. A conductor 22 passes through each tube as will hereinafter be described.

As best seen in FIGS. 2 and 3, each conductor 22 has an eyelet 24 welded near one end of the conductor. Eyelet 24 has a circular shoulder 26 upon which the lower edge of tube rests.

A mica spacer 30 having holes 32 therein of sufficient size to allow passage of tube 20 therethrough and spaced in accordance with the geometrical arrangement of tubes 20 comprises the first member of stacked gun assembly 10. Mica spacer 30 also is provided with a central aperture 34 of sufficient size to allow passage of electrical leads therethrough as will be described. Preferably, spacer 30 also has peripheral protrusions or ears 36 angularly spaced around its edge.

A cathode and grid subassembly 40 is located directly above spacer 30. Subassembly 40 comprises a hollow cylindrical grid cap 42 surrounding an insulator 44 centrally apertured to mount hollow cathode 46 therein. A heater 48 is positioned within cathode 46. Cap 42, as best seen in FIG. 4, is dimensioned to have an outer diameter of sufficient size to fit snugly between glass rods 20.

Spacing shim 50 comprises a glass disc of preselected thickness to properly space cathode assembly 40 from einzel lens 70. Shim 50 has openings 52 therein spacially conforming to the openings 32 allow rods 20 to pass therethrough and a central aperture 54 to provide passage for the electron beam from cathode assembly 40. I

Electrode disc 60, which is positioned immediately above shim 50, comprises the first electrode of einzel lens 70. Openings 62 within disc 60 conform geometrically with opening 52 in shim 50 to allow rods 20 to pass therethrough. A small central opening 64 comprises the first aperture of the unipotential or einzel lens used to focus the electron beam.

Immediately following disc 60 is a second mica spacer 30a which is formed identically to mica 30 and provides insulation between disc 60 and a focus cylinder of einzel lens 70. Focus cylinder 80 comprises a hollow metal cylinder completely open at both ends. Its outer diameter, like that of grid cap 42, is chosen to coincide with the geometric placement of rods 20 as shown in FIG. 5 enabling rods 20 to retain cylinder 80.

A third mica 30b is located at the opposite end of cylinder 70. Mica 30b is identical to mica 30 and, together with an identical fourth mica 30c, insulates an electrode disc from focus cylinder 80 and the subsequent deflection electrodes. Electrode disc 90 is identical to electrode disc 60. Electrode discs 60 and 90, together with cylinder 80, comprise the einzel focus lens 70.

Spaced between mica 30c and an identical fifth mica 30d are first deflection plates and 110. Deflection plates 100 and are respectively formed with lower flanges 102 and 112 and upper flanges 104 and 114 with flared out, upstanding, portions 108 and 118 therebetween. Openings 106 in deflection plate 100 and 116 in plate 110 allow passage of the rods 20 therethrough.

A second set of deflection plates 120 and are mounted on mica 30d at 90 axial displacement from plates 100 and 110. Plates 100, I10, 120, and 130 thus provide both X and Y deflection to the electron beam. Plate 120 is formed with a lower flange 122. Flange 122 has openings 126 thereon for passage of the rods 20 therethrough. Similarly, a flange 132 on plate 130 has openings 136 thereon for the passage therethrough of the other two rods 20.

Glass beads or cylinders 140 having an internal diameter slightly larger than the outer diameter of rods 20 are slipped over rods 20 to rest on flanges 122 and 132 respectively. Eyelets 24a, each having a circular shoulder 26a, are mounted on conductors 22 with the shoulder 26a resting on the upper surface of bead 140 and secured to conductor 22 as by welding or the like.

It can thus be seen that a unitary gun assembly 10 is formed wherein movement of the components along the axis of the gun assembly is prevented by the interaction of eyelets 24, grid-cathode assembly 40, focus cylinder 80 deflection electrodes 100-and 110, and eyelets 24a while lateral shifting is prevented by the glass rods 20 passing through the openings in the mica spacers and electrodes 60, 90, 100, I10, 120, and 130 while forming a cage-like retention for focus cylinder 80 and grid cathode assembly 40.

Gun assembly 10 is next attached to a stem comprising glass portion 152 having metallic pins 12 passing therethrough. Assembly 10 is mounted to stem 150 by welding metallic conductors 22 to appropriate pins 12 to provide both mechanical stability and subsequent external electrical connection. Additional appropriate electrical connections are made to the electrodes either directly from pins 12 or via conductors 22.

Gun assembly is now mounted into a cathode ray tube envelope 4 comprising a glass wall having a generally cylindrical neck portion with an internal diameter substantially equal to the diameter circumscribed by projections 36, 36a, 36b, 36c, and 36d on the respective mica spacers. These projections thereby frictionally engage the inner surface of the neck portion of envelope 4 to provide alignment of the gun assembly in tube 2 as well as to dampen or eliminate vibrations of the gun assembly by providing a type of shock mounting. It should be noted here, that the projections 36 need not be present on all the micas. The projections must be present, however, on at least two of the micas. Preferably, all of the micas are provided with the projections for manufacturing convenience as well as to obviate any difficulties should one of the projections on one of the micas be inadvertently damaged.

After insertion of gun assembly 10 into envelope 4, glass portion 152 on stem 150 is sealed to the end of the neck on envelope 4 and tube 2 is evacuated by a tubular opening (not shown) centrally provided in stem 150. It should be noted here that an opposite endwall 6 is sealed to envelope 4 in a previous step and a phosphor coating 8 placed on the inner surface of end wall 6.

The foregoing description of the invention thus describes a novel cathode ray tube having a rugged, economical, compact gun assembly which is easily assembled and provides a stable, aligned, gun assembly which is easily mounted yet sturdily retained in the neck of the tube by the projecting portions of the spacers. Costly additional parts and intermediate steps of manufacture, such as those previously referred to, are thereby eliminated or simplified.

What is claimed is:

l. A cathode ray tube comprising: a tubular envelope, at least a portion of which is of constant diameter, target means adjacent one end of said envelope, and electron beam discharge and control means in said envelope spaced apart from said target means and mounted in frictional contact with said constant diameter portion of said envelope, said discharge and control means comprising a stacked assembly comprising:

a. a first generally circular mica insulating disc having four openings of predetermined size therein, symetrically spaced from the center of said disc to define a circle of predetermined diameter circumscribed therebetween equal to the diagonals between said openings;

b. a cathode and grid subassembly including a grid cylinder having an external diameter substantially equal to said predetermined diameter;

c. einzel lens means comprising:

1. a pair of disc electrodes, each having a central opening therein and four openings symetrically spaced from the center of said central opening a distance equal to the spacings of the openings in said firstmica disc, each of said openings conforming to said predetermined size; and

2. a hollow cylindrical electrode insulatingly spaced between said disc electrodes by generally circular mica insulating discs substantially identical to said first mica disc, said cylinder having an outer diameter equal to said grid cylinder; d. an insulating spacer between said grid cylinder and said einzel lens of predetermined thickness to space said cathode a predetermined distance from said lens, said spacer having a central opening for passage of the electron beam therethrough and four openings symetrically spaced from the center of said central opening a distance equal to the spacing of the openings in said first mica disc and conforming in size to said openings; e. four hollow insulating tubes respectively in said four openings in said mica discs and said disc electrodes, each of said tubes having a diameter substantially equal to the size of said openings to provide a snug fit therein said tubes providing spaced apart line contact with said grid cylinder and said einzel lens cylinder to maintain the axial alignment of all of said discharge and control means; f. deflection means comprising: a

l. a first pair of plates equidistantly spaced from the axis of said beam to deflect the beam along one axis and having flanges thereon perpendicular to said beam axis with openings therein to receive said insulating tubes whereby said tubes maintain the axial alignment of said plates; and

2. a second pair of deflection plates equidistantly spaced from the axis of said beam to deflect the beam along an axis radially disposed from said one axis and having flange means thereon perpendicular to said beam axis with openings thereon to receive said insulating tubes therein to maintain the alignment of said second plates; and

g. metal rod means passing through said hollow insulating tubes and having eyelets on the extremities thereon contacting respectively said first mica disc and said flange means on said second pair of deflection plates to compress said discharge and control means therebetween;

whereby movement of said discharge and control means along the axis of said assembly is prevented by the interaction of said eyelets and said cylinders and lateral shifting of said discharge and control means is prevented by said tubes passing through the openings in said disc and flange members while retaining said cylinders in line contact therebetween. 

1. A cathode ray tube comprising: a tubular envelope, at least a portion of which is of constant diameter, target means adjacent one end of said envelope, and electron beam discharge and control means in said envelope spaced apart from said target means and mounted in frictional contact with said constant diameter portion of said envelope, said discharge and control means comprising a stacked assembly comprising: a. a first generally circular mica insulating disc having four openings of predetermined size therein, symetrically spaced from the center of said disc to define a circle of predetermined diameter circumscribed therebetween equal to the diagonals between said openings; b. a cathode and grid subassembly including a grid cylinder having an external diameter substantially equal to said predetermined diameter; c. einzel lens means comprising:
 1. a pair of disc electrodes, each having a central opening therein and four openings symetrically spaced from the center of said central opening a distance equal to the spacings of the openings in said first mica disc, each of said openings conforming to said predetermined size; and
 2. a hollow cylindrical electrode insulatingly spaced between said disc electrodes by generally circular mica insulating discs substantially identical tO said first mica disc, said cylinder having an outer diameter equal to said grid cylinder; d. an insulating spacer between said grid cylinder and said einzel lens of predetermined thickness to space said cathode a predetermined distance from said lens, said spacer having a central opening for passage of the electron beam therethrough and four openings symetrically spaced from the center of said central opening a distance equal to the spacing of the openings in said first mica disc and conforming in size to said openings; e. four hollow insulating tubes respectively in said four openings in said mica discs and said disc electrodes, each of said tubes having a diameter substantially equal to the size of said openings to provide a snug fit therein, said tubes providing spaced apart line contact with said grid cylinder and said einzel lens cylinder to maintain the axial alignment of all of said discharge and control means; f. deflection means comprising:
 1. a first pair of plates equidistantly spaced from the axis of said beam to deflect the beam along one axis and having flanges thereon perpendicular to said beam axis with openings therein to receive said insulating tubes whereby said tubes maintain the axial alignment of said plates; and
 2. a second pair of deflection plates equidistantly spaced from the axis of said beam to deflect the beam along an axis 90* radially disposed from said one axis and having flange means thereon perpendicular to said beam axis with openings thereon to receive said insulating tubes therein to maintain the alignment of said second plates; and g. metal rod means passing through said hollow insulating tubes and having eyelets on the extremities thereon contacting respectively said first mica disc and said flange means on said second pair of deflection plates to compress said discharge and control means therebetween; whereby movement of said discharge and control means along the axis of said assembly is prevented by the interaction of said eyelets and said cylinders and lateral shifting of said discharge and control means is prevented by said tubes passing through the openings in said disc and flange members while retaining said cylinders in line contact therebetween.
 2. a hollow cylindrical electrode insulatingly spaced between said disc electrodes by generally circular mica insulating discs substantially identical tO said first mica disc, said cylinder having an outer diameter equal to said grid cylinder; d. an insulating spacer between said grid cylinder and said einzel lens of predetermined thickness to space said cathode a predetermined distance from said lens, said spacer having a central opening for passage of the electron beam therethrough and four openings symetrically spaced from the center of said central opening a distance equal to the spacing of the openings in said first mica disc and conforming in size to said openings; e. four hollow insulating tubes respectively in said four openings in said mica discs and said disc electrodes, each of said tubes having a diameter substantially equal to the size of said openings to provide a snug fit therein, said tubes providing spaced apart line contact with said grid cylinder and said einzel lens cylinder to maintain the axial alignment of all of said discharge and control means; f. deflection means comprising:
 2. a second pair of deflection plates equidistantly spaced from the axis of said beam to deflect the beam along an axis 90* radially disposed from said one axis and having flange means thereon perpendicular to said beam axis with openings thereon to receive said insulating tubes therein to maintain the alignment of said second plates; and g. metal rod means passing through said hollow insulating tubes and having eyelets on the extremities thereon contacting respectively said first mica disc and said flange means on said second pair of deflection plates to compress said discharge and control means therebetween; whereby movement of said discharge and control means along the axis of said assembly is prevented by the interaction of said eyelets and said cylinders and lateral shifting of said discharge and control means is prevented by said tubes passing through the openings in said disc and flange members while retaining said cylinders in line contact therebetween. 